Measuring Earthquakes

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Vocab: Focus- the pint beneath earth's surface
Epicenter- the point directly above the surface
Seismic Waves- vibrations that travel through earth carrying energy
P Waves- Earthquake waves that expand and compress the ground
S Waves- Earthquake waves that vibrates side to side as well as up and down
Surface Waves- When P Waves and S Waves reach the surface some turn into surface waves
Magnitude- A measurement of earthquake strength based on seismic waves
Mercalli Scale- developed to rate earthquakes
Richter Scale- A rating of the size of seismic waves
Moment Magnitude Scale- a rating system that estimates the energy from an earthquake

Outline

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Seismic Waves

• like a drum
  • cause vibrations during an earthquake
    • vibrations travel through earth
      • carries energy
        • move like ripples in ponds

Primary Waves

• earthquake waves
  • waves that expand like an accordion
    • first waves for earthquake
      • compress and expand ground

Secondary Waves

• comes after P Waves
  • vibrate the earth
    • side to side
      • up and down

Surface Waves

• move slowly, much slower than P & S waves
  • cause a lot of damage
    • P & S Waves form them

Detecting Seismic Waves

• a good detector for earthquakes is the seismograph
  • seismograph is used to draw the waves while an earthquake is occurring
    • records ground movement

Measuring Earthquakes

• magnitude is a measurement for earthquakes

The Mercalli Scale

• describes how an earthquake affects people and buildings
  • is not very precise about its measurement
    • describes how an earthquakes affect people and buildings
      • is not very precise about its measurement

The Richter Scale

• rates Seismic Waves
  • many geologist use the Richter Scale
    • used in modern times

The Moment Magnitude Scale

• rates earthquakes sizes
  • measures every earthquake's magnitude
    • rates distance of earthquake

Locating the Epicenter

• geologists use seismic waves to determine an earthquake's epicenter
  • the difference between P and S waves depend on how far an earthquake is
    • epicenter is the point where the most shaking occurs

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